I've started stringing and using the Professional XP Plus machine. I do the mains ok.. but when I get onto the crosses towards the end, the string always snaps on me. It's when I try and put the string through a hole and the outside of the hole is covered with a mains string. Not sure if I've explained that right.. When I put the string through the hole, a string on the outside covers it, so I end up having to use some pliers or that long pointy thing to try and move the outside string up or down a bit so I can pass through the hole. The string is so tight though I end up having to use too much force and it snaps, forcing me to start from the beginning again. Stringing at 23lbs. Is there any techniques or special tools to help this?